Kate Middleton and Prince William broke royal protocol when they were dating. The couple is pictured during a visit to Blackpool, England on March 6, 2019. Chris Jackson/Getty Images

They may follow royal protocol most of the time, but that doesn’t mean Kate Middleton and Prince William have always followed the rules.

In the book “Harry: Life, Loss, and Love,” biographer Katie Nicholl revealed that there was a big difference between the way the Duke and Duchess of Cambridge handled their relationship during Prince William’s military career and that it directly contrasted with the way Prince Harry’s own relationship with Chelsea Davy was handled at the same time.

While Middleton lives with William in a rented cottage during those days, despite the move breaking protocol, Davy refused to make the same changes, which it’s believed led to their eventual split.

“William and Kate’s relationship was strong and committed, and there were rumors among their friends that an engagement was imminent,” Nicholl wrote. “William, who was stationed at RAF Valley in Anglesey, was training to fly Sea King helicopters at the time. Both brothers had agreed that their military careers were to be their priorities for the foreseeable future, but while Harry’s military commitments had taken their toll on his romance with Chelsy, Kate was prepared to make sacrifices that Chelsey simply wasn’t.”

“In a breach of royal protocol that showed just how modern their courtship was, he and Kate were living together in a rented cottage close to William’s base, Kate taking on, and enjoying, life as an ‘RAF wife,’” she added. “During the days, as William trained, Kate filled her time taking photographs, one of her hobbies, and working for her parents’ party-planning family firm on an ad-hoc basis.”

Still, despite the couple’s decision not to follow protocol with that living arrangement, everything worked out well for them in the end, as they went on to become engaged in November 2010 and married in April 2011. They have since also welcomed three children together as well.

Harry’s romance with Davy fizzled after the wedding after she realized royal life wasn’t for her. He went on to marry Meghan Markle in May 2018, and the couple is expecting their first child together any day.